1. Field of the Invention
This invention relates to large film cassettes for obtaining images on photosensitive film from radioactive or radiation emitting specimens and their use. A film cassette designed to receive photosensitive film in a light protective envelope and maintain lighttight integrity while removing the protective envelope includes means for bringing a light emitting enhancer screen into intimate contact with the photosensitive film during exposure to x-ray photography. The back of the photosensitive film may be brought into intimate contact with a sheet of specimen-containing radioactive or radiation generating material.
2. Description of the Prior Art
In large format radiography (e.g. 8.times.10 or 10.times.12) it is standard practice to load the film into a holder or cassette. The cassette, which is typically lighttight when loaded with film, facilitates storage, handling and processing of the film.
Cassettes have proven to be particularly useful in radiography using self-developing film. Daylight pre-loading of the cassette with the film handling convenience and relatively short time periods to prepare for exposure and processing are all highly desirable qualities. For x-ray applications the cassette preferably includes a light-enhancing screen or surface which has a layer of phosphors which emits visible light and ultraviolet light when exposed to radionucleotides including x-rays. The photosensitive layer of the film unit is held in close and continuous contact with the phosphor layer so that the x-ray induced light of phosphors intensifies the image to be recorded on the film.
In the science of audioradiography, specimen sheets which have been provided with a radioactive material are presently inserted directly into film cassettes designed for x-ray photography. This operation is presently done in a darkroom to prevent fogging (partial exposure) of the x-ray film. Such sheets may consist of the product of electrophoresis gel separation of cell tissues into varying molecular weights. The products of such separation are treated with radioactive isotopes or elements which have an affinity for the specimen (i.e. such as an affinity for DNA pairings). Such gels are transferred to a membrane and dried. Although the radiation level is low a desired photographic image may be obtained in an x-ray cassette.